We propose to investigate: (1) the identity of the protein and RNA components of peptidyl transferase; (2) the topography of 5S, 16S and 23S RNA and their sites of interaction with specific ribosomal proteins; (3) the involvement of 16S RNA in tRNA binding; (4) the interaction of protein S1 with natural and synthetic polynucleotides; (5) reversible covalent crosslinking of ribosomal RNA with ribosomal proteins.